Stuffing machines of the type shown in U.S. Pat. No. 3,191,222 are commonly used in the manufacture of frankfurters and the like. In use, a hollow tubular shirred casing stick is located on the stuffing horn and is deshirred and stuffed with a food emulsion discharged from the horn. positioned at the discharge end of the stuffing horn is a rotatable chuck member made of plastic. As the casing deshirrs and fills with the food emulsion, it passes longitudinally through a cylindrical bore in the chuck. The chuck forces the filled casing into a smaller diameter during longitudinal movement through the chuck. The chuck is rotatably driven so it transfers a torque to the casing for twisting the stuffed casing into links. Twisting into links is accomplished in association with the pinchers of a conventional linking apparatus located downstream from the stuffing horn and chuck.
The chuck member also is designed to impose a longitudinal drag or "holdback" on the casing moving longitudinally through its bore. Without this holdback the food emulsion will not tightly stuff into the casing. The holdback on the casing is provided by longitudinal flutes spaced circumferentially around the bore of the conventional chuck member. These flutes. as shown in U.S. Pat. Nos. 3,115,668 and 3,191,222 extend substantially the full length of the chuck bore and provide the longitudinal dragging action to casing within the bore.
The inlet end of the chuck bore is inwardly tapered from a first relatively larger diameter to a second relatively smaller diameter at a location intermediate the inlet end and the discharge end of the bore. This tapered inlet receives the front end of the shirred casing stick and the flutes in this section grip and rotate the stick while casing deshirrs and is drawn from the front end of the stick during stuffing. The stuffed casing then passes through the smaller diameter downstream of the intermediate location where it is deformed and gripped by the flutes pressing inwardly against the stuffed casing. The flutes, by gripping the stuffed casing, allow the chuck to transmit torque to the stuffed casing thereby rotating the stuffed casing for twisting it into links.
The flutes must be properly sized to provide sufficient holdback for stuffing yet must not apply so much holdback that the casing will be filled with an excessive amount of emulsion and burst. As previously indicated, the flutes also must grip the casing to provide the needed torque transmission for twisting and linking the filled casing.
It has always been a compromise to design a chuck with flutes which provide sufficient gripping for adequate torque transmission without gripping so tightly that there is excessive holdback as this could result in overstuffing and possible breakage of the casing. The conventional practice has been to design a chuck which provides only adequate holdback rather than risk overstuffing. Accordingly, since the flutes are subject to wear, the practice has been to replace the chucks as soon as the flute wear is such that the casing is not stuffed to size or abnormal twists and links are formed. Typically, the chucks are considered expendable by the meat packing houses, and are replaced every day or so. This represents a considerable maintenance cost.
One proposed solution to the chuck wear problem is described in U.S. Pat. No. 4,670,942. The chuck described in this Pat. has a set of free-wheeling rollers journaled to the chuck body adjacent the outlet end of the bore. These rollers which surround the outlet are arranged to grip and rotate the stutted casing as it leaves the bore without correspondingly increasing the longitudinal drag on the casing.
Another problem with the conventional chucks is that they are unsuitable for use with casings having outer coatings with substantially higher coefficient of friction values than the typical uncoated nonreinforced cellulosic casing conventionally used to stuff frankfurters. One such coating is wood-derived tar-depleted liquid smoke impregnated in the cellulosic casing outer wall. as for example described in U.S. Pat. No. 4,505,939. The surface of a liquid smoke impregnated cellulosic casing of this type has a dynamic coefficient of friction (COF) of at least 0.46, whereas, the surface of typical uncoated cellulosic casing has a dynamic COF on the order of 0.33.
When the liquid smoke impregnated nonreinforced cellulosic casings are stuffed on a conventional frankfurter stuffing machine using a rotatable plastic chuck having end-to-end flutes as described in U.S. Pat. No. 3,191,222, the higher COF creates a greater longitudinal drag or holdback so that the resulting frankfurter links are shorter and larger in diameter than the length of frankfurters made when using the lower COF uncoated nonreinforced cellulosic casings. Shorter frankfurter links are commercially unacceptable.